1. Field of the Invention
This invention relates to a vibration tester for screws and bolts in which the specimen is checked for looseness by subjecting it to impact or vibration.
2. Description of the Prior Art
In the prior art, various devices for testing the looseness of screws and bolts have been developed. A representative such tester is illustrated in FIGS. 1 and 2, which comprises a shaft 62, which may be mounted in a box 61, which is vertically vibrationally disposed. Onto the shaft 62 is fixedly mounted a jig 63 having a plurality of slits 64 formed therein. To test a specimen for looseness, it is inserted into the slits 64, as depicted in FIG. 2, and exposed to violent vibration by oscillating the shaft 2. The specimen has a sleeve 66. A bolt 67 is passed through the sleeve 66 and fixed in position with a nut 68 that is tightened against the bolt's head 67a. With this arrangement, the looseness of the nut 68 is measured by a strain gauge S fitted onto the sleeve 66.
These conventional vibration testers have been found universally unacceptable for application with all available sorts of nuts since they lack the ability to cause looseness in high-tension locking nuts.
It is this drawback of the prior art testers that gave rise to the present invention. It is therefore a primary object of the present invention to provide a vibration tester capable of testing a wide range of bolts and screws for looseness by subjecting them to strong impact.